CN101788569A - Optical fiber acceleration transducer probe and acceleration transducer system - Google Patents

Abstract

The invention provides an optical fiber acceleration sensor probe and an optical fiber acceleration sensor system based on phase carrier modulation technology. The system includes: laser light source, optical fiber, optical fiber coupler, optical fiber acceleration sensor probe, photoelectric detector, phase carrier modulation signal electronic demodulation system. The laser light source is a phase carrier modulated laser light source; the fiber coupler is respectively connected to the laser light source, the acceleration sensor probe and the photodetector through the optical fiber; the photodetector is connected to the electronic demodulation system of the phase carrier modulation signal through a wire or cable; The acceleration sensor probe includes: an acceleration detection structure, at least one back plate, an acceleration sensor frame and at least one optical fiber sensing head. The system of the present invention adopts a double-back plate structure and an optical fiber read-out detection method, so that the system is improved and enhanced in terms of impact resistance and overload performance, electromagnetic interference resistance, sensitivity and the like.

Description

A kind of optical fiber acceleration sensor probe and acceleration sensor system

technical field

The invention relates to the technical field of inertial sensors, in particular to an optical fiber acceleration sensor probe and an optical fiber acceleration sensor system based on phase carrier modulation.

Background technique

Acceleration sensor is a very important inertial sensing and measurement device, which is widely used in aerospace, vibration monitoring, industrial control, geophysical exploration and other fields. In recent years, with the development and maturity of MEMS (micro-electromechanical systems) technology, MEMS acceleration sensors have been widely used in automotive electronics and consumer electronics products due to their small size, light weight, low cost, and high integration. And further expand to the field of industrial application, has a broad market prospect.

The acceleration sensor realizes the measurement of the external acceleration by converting the sensed acceleration into an electrical signal output at a certain ratio. Traditional acceleration sensors are usually composed of sensitive elements, readout and amplification circuits, and metal casings. They have high sensitivity and stable performance, but their performance depends heavily on machining accuracy. Although the MEMS acceleration sensor has many advantages, its sensitivity still has a certain gap with the requirements of the industrial field, and the Q value is not easy to adjust. In the Chinese patent application with application number 200910087937.6, the applicant proposed an acceleration sensor structure using a mass block-elastic membrane-back plate-acoustic cavity, which improves the sensitivity of the acceleration sensor and can easily adjust the system Q value . However, the above acceleration sensors convert the external acceleration into electrical signals directly in the sensor head, so they are easily interfered by external electromagnetic noise, and are not suitable for applications in environments such as strong electric fields, strong magnetic fields, or strong radio frequency fields.

The acceleration sensor usually converts the external acceleration into the displacement of a movable part on the sensing head. The optical fiber acceleration sensor is a device that detects the displacement signal, converts it into a modulated optical signal, transmits it through an optical fiber, and then demodulates the modulated optical signal into an electrical signal. The fiber optic acceleration sensor generally includes two independent parts of the sensor head and the electronic circuit system, and the two parts are connected by an optical fiber. Since there is no conversion of electrical signals and no electronic circuits in the sensor head part, that is, the sensor head part neither generates electromagnetic signals nor is interfered by electromagnetic signals. Therefore, the fiber optic acceleration sensor can be used in strong electric fields, strong magnetic fields or In a strong radio frequency field environment. In addition, the fiber optic acceleration sensor also has the advantages of high sensitivity and resolution, wide frequency bandwidth, large dynamic range, and good low frequency response.

The modulation methods of optical fiber acceleration sensors generally include light intensity modulation, phase modulation and polarization modulation, etc. The acceleration sensor system using light intensity modulation is generally relatively simple, but in terms of sensitivity, signal-to-noise ratio and dynamic range indicators, there is no optical fiber with phase modulation. The accelerometer system is fine.

The optical fiber sensing system using phase carrier modulation has relatively good stability. For example, in the patent documents such as CN03200396.X, the optical fiber phase carrier modulation technology is proposed. For lasers, phase carrier modulation is achieved by winding an optical fiber on a piezoelectric vibrator, or pasting a self-focusing lens on a piezoelectric vibrator, and applying a sinusoidal signal of a specific frequency to the piezoelectric vibrator. However, this method is not available in the product Miniaturization and temperature stability still need to be improved.

In addition, the present applicant once proposed a fiber optic silicon micro-microphone system based on phase carrier modulation in Chinese patent application No. 200610112615.9. The system can better improve the sensitivity and anti-electromagnetic interference ability of the silicon micro-microphone. But the system is not suitable for sensors other than microphones.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of weak anti-electromagnetic interference ability, low sensitivity and resolution, and small dynamic range in the existing acceleration sensor technology, thereby providing a fiber optic acceleration sensor probe and a fiber optic acceleration sensor system based on phase carrier modulation technology . The system uses phase carrier modulated laser light source to realize the direct modulation of optical signal. Within a certain power range, the output laser frequency is proportional to the current intensity applied to the light source. And by adopting double-back plate structure and optical fiber readout detection method, the system has been improved and improved in terms of impact resistance and overload performance, anti-electromagnetic interference, and sensitivity.

To achieve the purpose of the above invention, the present invention provides a fiber optic acceleration sensor probe, which is characterized by comprising: an acceleration detection structure, at least one back plate, an acceleration sensor frame and at least one fiber optic sensing head.

The acceleration detection structure is located at the center of the acceleration sensor probe, and its composition includes: a proof mass, an elastic member positioned around the proof mass and a supporting member, which convert the sensed acceleration into a displacement of the proof mass, and the proof mass The block and the elastic part can adopt the mass block-spring structure of the traditional capacitive acceleration sensor, or the mass block-elastic beam or mass block-elastic diaphragm structure of the MEMS acceleration sensor (including the porous and non-porous elastic diaphragm), Wherein, the detection mass is located at the center of the entire acceleration detection structure, the two ends of the elastic member are respectively connected to the detection mass and the support member, and the elastic member is center-symmetrical around the detection mass distribution, the role of the support component is to support the acceleration detection structure and fix it on the acceleration sensor frame.

The detection mass is parallel to the back plate up and down, an air gap is formed therebetween, and a reflective film area is made on the surface of the proof mass on the side opposite to the back plate, and the reflective film area is located on the detection mass. center of the block or cover the entire surface of the proof mass.

The back plate is a relatively rigid plate whose boundary is fixed on the frame of the acceleration sensor, and its material may be a printed circuit board, a silicon wafer or a glass plate. Damping holes of specific size and distribution are made on the back plate to adjust the damping. One side of the back plate is made with limited protrusions to prevent overload and adhesion. The center of the back plate is also made with a transparent hole. The optical hole is used to transmit incident and reflected laser light; in addition, an acoustic cavity is formed between the back plate and the acceleration sensor frame, and the acoustic cavity is a cavity or two connected or disconnected cavities for forming a flow The gas circuit improves the frequency response of the system; the area of the reflective film on the proof mass is directly opposite to the light-transmitting hole on the back plate, and the size of the area of the light-reflecting film is larger than the size of the light-transmitting hole. When there are two back pole plates, the two back pole plates are arranged symmetrically up and down relative to the proof mass block, the structures of the two back pole plates are the same or different, and damping holes and limiting protrusions are made on them. As well as the light-transmitting hole, the two back plates respectively form two upper and lower acoustic cavities with the acceleration sensor frame, and form two upper and lower air gaps with the detection mass, thus forming a back plate-damping hole - Acoustic cavity structure to adjust the damping and Q-value of the system.

In addition, the acceleration detection structure can also be provided with driving electrodes, which are located on the periphery of the reflective film area on one or the upper and lower surfaces of the detection mass. If the upper and lower surfaces of the detection mass are provided, the two The driving electrodes are distributed mirror-symmetrically with respect to the detection mass, and at the same time, driving electrodes are also made on the surface of the back plate opposite to the detection mass, and the driving electrodes on the detection mass are as far as possible to form a The driving electrode pair provides electrostatic force for the detection mass, which is used to adjust the position of the mass, introduce mechanical feedback, and provide a reverse electric power to achieve overload recovery when overload is adhered.

In addition, the acceleration detection structure can also be made of a single crystal oriented silicon wafer through MEMS process steps including high temperature oxidation, photolithographic patterning, dethermal oxygen removal and bulk etching. The single crystal silicon acceleration detection structure includes three parts: a single crystal silicon support structure, a single crystal silicon elastic vibrating membrane and a single crystal silicon acceleration detection mass block, wherein the single crystal silicon acceleration detection mass block and the single crystal silicon elastic vibration The membrane has the same geometric center, and the two are processed by volume etching of the single crystal oriented silicon wafer, and the inner boundary of the single crystal silicon elastic vibration membrane is connected with the outer boundary of the single crystal silicon acceleration detection mass , the outer boundary of the single crystal silicon elastic diaphragm is connected to the inner boundary of the single crystal silicon support structure, the single crystal silicon support structure is used to support the acceleration detection structure and is attached to the back plate, and its thickness is the same as that of the single crystal silicon support structure The silicon slices with the same crystal orientation; the bottom view of the single crystal silicon supporting structure, the single crystal silicon elastic vibrating membrane and the single crystal silicon acceleration detection mass is any shape including a circle, a rectangle, a square, and a regular hexagon; the single crystal The silicon acceleration detection structure is mirror-symmetrical to the central plane in the thickness direction, wherein the thickness of the single crystal silicon support structure is equal to the thickness of the single crystal oriented silicon wafer, and the thickness of the single crystal silicon acceleration detection mass is smaller than that of the single crystal silicon acceleration detection mass. The thickness of the crystal-oriented silicon chip is thin, and the vertical distance between the upper and lower surfaces of the wafer and the upper and lower surfaces of the single crystal silicon supporting structure is about 2-100 microns, and the thickness of the single crystal silicon elastic vibration film is 5-500 microns.

The optical fiber sensing head includes a gradient lens and a pigtail, the pigtail is installed at the tail of the gradient lens, the gradient lens is installed on the acceleration sensor frame, or is installed on an additional Fizeau interference cavity support, When installing, make the exit end face of the gradient lens face the light transmission hole on the back plate and the reflective film area on the detection mass block, and ensure that the exit end face is parallel to the reflective film area, and the reflective film area will pass through the gradient The laser light incident on the lens is reflected back, thereby modulating the phase of the incident light, and a cylindrical Fizeau interference cavity is formed between the exit surface of the gradient lens and the region of the reflective film. Here, the Fizeau interference cavity support can be installed on the side of the back plate that is not made with a limited convex contact, or on other positions such as the acceleration sensor frame, as long as the gradient lens exit surface is guaranteed The distance from the reflective film area, that is, to ensure that the length of the Fizeau interference cavity meets the requirements.

When there are two optical fiber sensing heads, the structures of the two optical fiber sensing heads are exactly the same, and they are arranged on the frame of the acceleration sensor relatively symmetrically with respect to the detection mass, or are arranged on an additional Fizeau interference cavity bracket, and make the exit end face of the gradient lens face the light transmission hole on the back plate and the reflective film area on the proof mass block, and ensure that the exit end face is parallel to the reflective film area, and the upper and lower two optical fiber sensors The two upper and lower Fizeau interference cavities formed between the gradient lens exit surface of the head and the region of the reflective film have exactly the same length.

In addition, the optical fiber acceleration sensor system based on phase carrier modulation provided by the present invention includes: a laser light source, an optical fiber, a fiber coupler, an acceleration sensor probe, a photodetector, and an electronic demodulation system for phase carrier modulation signals.

The laser light source is a phase carrier modulated laser light source; the optical fiber includes an input fiber, a transmission fiber and an output fiber; the fiber coupler is connected to the phase carrier modulated laser light source through the input fiber, through the The transmission optical fiber is connected with the acceleration sensor probe, and is connected with the photodetector through the output optical fiber; the photodetector is connected with the phase carrier modulation signal electronic demodulation system through a wire or cable; the acceleration sensor probe It includes at least one gradient lens and an acceleration detection mass block with a reflective film area. The exit end face of the gradient lens is placed in parallel with the reflective film area on the acceleration detection mass block to form a laser Fizeau interference cavity.

In the above technical solution, the phase-carrier modulated laser light source includes at least one semiconductor laser and an oscillator that generates a modulation current. Within the rated luminous power range, the laser light frequency output by the semiconductor laser varies linearly with the modulation current.

In the above technical solution, the input optical fiber, the output optical fiber and the transmission optical fiber are all single-mode optical fibers.

In the above technical solution, the optical fiber coupler is a coupler that splits the injection beam into two beams of light with equal light intensity.

In the above technical solution, the photodetector is a photoelectric conversion circuit composed of PIN photodiodes.

In the above technical solution, the phase carrier modulation signal electronic demodulation system is an electronic signal processing system that demodulates the corresponding acceleration signal in the carrier modulation signal.

In the above technical solution, the acceleration sensor probe includes: an acceleration detection structure, at least one back plate, an acceleration sensor frame and at least one optical fiber sensing head.

Wherein, the acceleration detection structure is located at the center of the acceleration sensor probe, and its composition includes: a proof mass, an elastic component located around the proof mass and a supporting component, which convert the sensed acceleration into a displacement of the proof mass, the The detection mass and the elastic part can adopt the mass-spring structure of the traditional capacitive acceleration sensor, or the mass-elastic beam or mass-elastic diaphragm structure of the MEMS acceleration sensor (including the porous and non-porous elastic diaphragm ), wherein the proof mass is located at the center of the entire acceleration detection structure, the two ends of the elastic member are respectively connected to the proof mass and the support member, and the elastic member surrounds the proof mass distributed centrally. The function of the supporting component is to support the acceleration detection structure and fix it on the acceleration sensor frame.

The detection mass is parallel to the back plate up and down, an air gap is formed therebetween, and a reflective film area is made on the surface of the proof mass on the side opposite to the back plate, and the reflective film area is located on the detection mass. center of the block or cover the entire surface of the proof mass.

The back plate is a rigid plate whose boundary is fixed on the acceleration sensor frame, and damping holes of a specific size and distribution are made on the back plate to adjust damping, and one side of the back plate is made There are limited convex contacts to prevent overload and adhesion. In addition, a light-transmitting hole is made in the center of the back plate to transmit incident and reflected laser light; an acoustic cavity is formed between the back plate and the acceleration sensor frame. The acoustic cavity is a cavity or two connected or disconnected cavities, which are used to form a flow gas circuit and improve the frequency response of the system; Yes, and the size of the reflective film area is larger than the size of the light hole.

The optical fiber sensing head includes a gradient lens and a pigtail, the pigtail is installed at the tail of the gradient lens, the gradient lens is installed on the acceleration sensor frame, or is installed on an additional Fizeau interference cavity support, When installing, make the exit end face of the gradient lens face the light transmission hole on the back plate and the reflective film area on the detection mass block, and ensure that the exit end face is parallel to the reflective film area, and the reflective film area will pass through the gradient The laser light incident on the lens is reflected back, thereby modulating the phase of the incident light, and a cylindrical Fizeau interference cavity is formed between the exit surface of the gradient lens and the region of the reflective film. Here, the Fizeau interference cavity support can be installed on the side of the back plate that is not made with a limited convex contact, or on other positions such as the acceleration sensor frame, as long as the gradient lens exit surface is guaranteed The distance from the reflective film area, that is, to ensure that the length of the Fizeau interference cavity meets the requirements.

In addition, in the above technical solution of the optical fiber acceleration sensor system based on phase carrier modulation, the structure of the optical fiber acceleration sensor probe may have two back plates and two optical fiber sensing heads. Wherein, the two back pole plates are arranged symmetrically up and down relative to the detection mass block, and the two back pole plates have the same structure, and are made with damping holes, limiting protrusions and light transmission holes, and the two back pole plates are respectively connected to the Two upper and lower acoustic cavities are formed between the acceleration sensor frame, and two upper and lower air gaps are formed between the detection mass, thereby forming a back plate-damping hole-acoustic cavity structure to adjust the damping and Q value of the system . The upper and lower surfaces of the detection mass block are provided with reflective film areas, which are mirror-symmetrically distributed with respect to the detection mass block. Moreover, the structures of the two optical fiber sensor heads are identical, and they are arranged on the frame of the acceleration sensor symmetrically with respect to the detection mass, or on the additionally added Fizeau interference cavity support, and make the gradient lens The exit end face is directly opposite to the light transmission hole on the back plate and the reflective film area on the detection mass, and the exit end face is parallel to the reflective film area. The upper and lower Fizeau interference cavities formed between the regions have exactly the same length. The fiber optic acceleration sensor system composed of this structure works in a differential mode. When the sensor feels the effect of external acceleration, the mass block in the fiber optic acceleration sensor probe moves upward or downward, making the length of the upper and lower Fizeau interference cavities change. Change the phase modulation of the incident laser light through the two gradient lenses respectively. The modulated laser is input into two transmission fibers as the sensing signals of the two signal arms, and the two are coupled by the fiber coupler and enter the output fiber for interference, and are converted into electrical signals by the photodetector and enter The carrier modulation signal is demodulated in an electronic demodulation system.

In addition, in the above-mentioned technical solution of the optical fiber acceleration sensor system based on phase carrier modulation, the acceleration detection structure in the structure of the optical fiber acceleration sensor probe can also include a driving electrode, which is arranged on one or two upper and lower sides of the proof mass. If the periphery of the reflective film area on the surface is provided on both the upper and lower surfaces of the detection mass, the two driving electrodes are mirror-symmetrically distributed relative to the detection mass. In addition, in this structure, driving electrodes are also made on the surface of the back plate opposite to the detection mass, which is as direct as possible to the driving electrodes on the detection mass to form a pair of driving electrodes, providing a static state for the detection mass. Electricity is used to adjust the position of the mass block, introduce mechanical feedback, and provide an electric power in the opposite direction to achieve overload recovery when overload is adhered. In addition, in this structure, the optical fiber sensor head has one or two, which are arranged on the frame of the acceleration sensor, or arranged on the additionally added Fizeau interference cavity support, and make the exit end face of the gradient lens It is directly opposite to the light-transmitting hole on the back plate and the reflective film area on the detection mass block, and ensures that the exit end surface is parallel to the light-reflective film area; The lengths of the upper and lower Fizeau interference cavities formed between the gradient lens exit surfaces of the upper and lower optical fiber sensing heads and the region of the reflective film are exactly the same. The optical fiber acceleration sensor system composed of the above structure works in a feedback mode. At this time, it is necessary to add a feedback control circuit module in the electronic demodulation system of the phase carrier modulation signal, and connect the driving electrodes on the fiber optic acceleration sensor probe through this module . The phase-carrier modulation signal electronic demodulation system generates a voltage feedback signal proportional to the received signal amplitude and inputs it to each driving electrode on each fiber optic acceleration sensor probe while performing demodulation.

The beneficial effects of the fiber optic acceleration sensor probe and the fiber optic acceleration sensor system based on the phase carrier modulation technology of the present invention are:

(1) The optical fiber acceleration sensor probe of the present invention has no electronic circuit, can be connected by optical fiber when in use, it neither produces electromagnetic signal, also is not disturbed by electromagnetic signal, therefore, can be applied to strong electric field, strong magnetic field or strong radio frequency field environment.

(2) The present invention adopts the laser of phase carrier modulation as light source and has applied gradient lens in the sensing probe of optical fiber acceleration sensor, therefore, the present invention is better than the sensor that adopts light intensity modulation in aspects such as sensitivity, dynamic range and signal-to-noise ratio a lot of.

(3) The present invention adopts a double back plate structure, which limits the movement range of the acceleration detection mass, greatly improving the impact resistance of the system; the electrodes on the back plate can provide electrostatic force for adjusting the position of the mass , Introduce mechanical feedback and provide a reverse direction of electric power to achieve overload recovery when overload is adhered.

(4) the optical fiber acceleration sensor probe of the present invention adopts the back plate-damping hole-acoustic cavity structure, the acoustic hole size and the density on the back plate can adjust the damping and frequency response of the system; the convex contact on the back plate can be Prevent sticking when overloaded.

(5) The optical fiber acceleration sensor probe of the present invention is easy to detect in a differential manner, and is also easy to introduce a feedback mechanism, which can further improve its performance such as sensitivity, dynamic range, and signal-to-noise ratio.

(6) The acceleration detection structure of the present invention is manufactured by MEMS technology, and has been improved and improved in aspects such as sample gap control and device consistency.

Description of drawings

Fig. 1 is a block diagram of the optical fiber acceleration sensor system based on phase carrier modulation of the present invention.

Fig. 2 is a structural schematic diagram of an embodiment of the fiber optic acceleration sensor probe in the fiber optic acceleration sensor system of the present invention.

Fig. 3 is a block diagram of the differential optical fiber acceleration sensor system based on phase carrier modulation of the present invention.

Fig. 4 is a structural schematic diagram of another embodiment of the fiber optic acceleration sensor probe in the fiber optic acceleration sensor system of the present invention.

Fig. 5 is a structural schematic diagram of another embodiment of the fiber optic acceleration sensor probe in the fiber optic acceleration sensor system of the present invention.

Fig. 6 is a structural schematic diagram of another embodiment of the fiber optic acceleration sensor probe in the fiber optic acceleration sensor system of the present invention.

Drawing logo:

100 phase carrier modulated laser light source

200, 400, 600 Coupling fiber

300 fiber optic coupler

700 photodetectors

800 phase carrier modulation signal electronic demodulation system

500 fiber optic acceleration sensor probe

510 Acceleration sensor head

511 Proof mass

512 Elastic components (including springs, elastic beams, elastic vibrating membranes with or without holes or other devices providing elastic restoring force)

513 Acceleration sensor head supporting part

516, 517 The reflective film area on the sensor head (mostly set at the center of the mass block)

518, 519 Drive electrodes on the sensing head (set on the periphery of the reflective film area)

520 accelerometer back plate

521 Acoustic holes on back plate

522 The limit protrusion on the back plate

523 Light-transmitting holes on the back plate

524 Drive electrodes on the back plate (opposite to the drive electrodes on the sensing head)

525, 528 vias

526, 529 leads and pads

527 Drive electrode on the back plate (opposite to the voltage of electrode 524, providing electrostatic force for the proof mass block)

Another back plate for the 530 accelerometer

540 acceleration sensor frame (or package)

541 Acceleration sensor housing

542 Air gap between sensor head 510 and back plate 520

543 Air gap between sensing head 510 and back plate 530

544 Acoustic cavity between back plate 520 and housing 541

545 Acoustic cavity between back plate 530 and housing 541

550 fiber optic detection head

551 Fizeau interference cavity holder

552 gradient lens

553 gradient lens exit facet

554 Pigtail

555 Fizeau interference cavity

560 fiber optic detection head, the same structure as the detection head 550

Detailed ways

A fiber optic acceleration sensor probe and a fiber optic acceleration sensor system based on phase carrier modulation technology of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

FIG. 1 is a schematic block diagram of an embodiment of an optical fiber acceleration sensor system based on phase carrier modulation of the present invention. As shown in Fig. 1, a kind of optical fiber acceleration sensor system 1000 based on phase carrier modulation of the present invention includes: laser light source 100 of phase carrier modulation, input optical fiber 200, optical fiber coupler 300, transmission optical fiber 400, optical fiber acceleration sensor probe 500 , an output optical fiber 600, a photodetector 700 and an electronic demodulation system 800 for carrier modulation signals. The fiber coupler 300 is connected with the phase carrier modulated laser light source 100, the fiber acceleration sensor probe 500 and the photodetector 700 respectively through the input fiber 200 and the transmission fiber 400 And the output optical fiber 600 is connected. The photodetector 700 is connected with the phase carrier modulation signal electronic demodulation system 800 through wires or cables.

The working principle of the present invention is as follows: the optical fiber acceleration sensor probe 500 at least includes a gradient lens (also called self-focusing lens) and an acceleration detection mass with a reflective film area (or called reflective spot), and the exit of the gradient lens The end face and the reflective film area on the acceleration detection mass are placed in parallel, and a columnar space is formed between the exit end face and the reflective film area, which is called a laser Fizeau interference cavity. The gradient lens is used as a collimating lens for outgoing light and a converging lens for reflecting light from the reflective film area on the acceleration detection mass block. The outgoing end surface of the gradient lens is coated with a reflective film to reflect a part of the incident light as the reference arm (that is, the path that the optical signal does not contain the sensing information) optical signal, while the signal arm (that is, the optical signal that contains the sensing information) The length of the path traveled) is twice the distance between the reflective film area on the acceleration detection mass and the exit end face of the gradient lens. When the acceleration detection mass feels the external acceleration, the reflective film area on it will produce a slight displacement, and the slight displacement will modulate the phase of the reflected light. In this way, the optical signal from the reference arm and the phase-modulated optical signal from the signal arm form interference, and the generated interference optical signal is transmitted to the The photodetector 700 is converted into a carrier-modulated electrical signal, and the electrical signal is demodulated by the phase-carrier modulated signal electronic demodulation system 800 to obtain an electrical signal corresponding to the acceleration value. In order to improve the sensitivity of the fiber optic acceleration sensor system 1000 and expand its dynamic range, the incident light signal of the fiber optic acceleration sensor probe 500 comes from the laser light source 100 modulated by the phase carrier.

The laser light source 100 modulated by the phase carrier includes at least one highly stable laser (such as a DFB semiconductor laser) and an oscillator that generates a modulation signal, and the wavelength (frequency) of the laser is related to the output optical power, that is, to the injected excitation related to current. Within a certain luminous power range, the optical frequency output by the laser light source varies approximately linearly with the modulation current. The high stability laser and the oscillator together generate a periodically modulated laser signal. When the carrier-modulated laser signal is output, if the input fiber 200 is a polarization-maintaining fiber, it can be transmitted to the input fiber 200 after passing through a polarizer. Generally, the polarizer can also be omitted.

The input optical fiber 200, output optical fiber 600 and transmission optical fiber 400 are single-mode optical fibers, which may be polarization-maintaining single-mode optical fibers or non-polarization-maintaining single-mode optical fibers. The role of these fibers is to ensure low-loss transmission of optical signals.

The fiber coupler 300 is a generalized optical coupling device, its role is to couple the optical signal from the phase carrier modulated laser light source 100 into the transmission fiber 400, and accelerate the signal from the fiber The reflected optical signal of the sensor probe 500 is coupled into the output optical fiber 600 . The fiber coupler 300 splits the injected beam into two beams with a light intensity of 1:1, and it can be a 2x1 fiber coupler or a 2x2 fiber coupler. For the case of using a 2x2 fiber coupler, a bundle of light injected into the 2x2 fiber coupler is an optical signal from the phase carrier modulated laser light source 100, which passes through the input fiber 200 and the 2x2 fiber coupler connection, one of the two separated beams of light enters the transmission fiber 400, and the propagation direction of the light is from the 2x2 optical fiber coupler to the fiber optic acceleration sensor probe 500, while the other beam of separated light does not Use (not shown in accompanying drawing 1 of the present invention), can be connected to the light absorbing end, also can not connect anything. Another beam of injected light is reflected light from the fiber optic acceleration sensor probe 500, the propagation direction of the light is from the fiber optic acceleration sensor probe 500 to the 2x2 fiber optic coupler, two beams of light are separated, and one beam enters the An input fiber 200 and a bundle enters the output fiber 600 .

The photodetector 700 is a generalized light intensity detection device, which converts the received light signal into an electrical signal proportional to the light intensity. It is generally a photoelectric conversion circuit composed of PIN photodiodes.

The phase-carrier modulation signal electronic demodulation system 800 is a generalized electronic signal processing system, and its function is to demodulate the signal of a specific frequency in the phase-carrier modulation signal. There are generally two schemes that can complete demodulation, that is, analog electronic circuit demodulation scheme and digital signal processing DSP demodulation scheme. The demodulation scheme of the described analog electronic circuit refers to the analog operations such as multiplication, filtering, differentiation and integration of the analog circuit to complete the demodulation of the phase carrier modulation signal; the described digital signal processing DSP demodulation scheme refers to the analog signal After A/D conversion for quantization, digital demodulation is realized through digital signal processing DSP software operation, and then digital demodulation signal is converted into corresponding analog demodulation signal through D/A conversion.

From the working principle of the optical fiber acceleration sensor with phase carrier modulation given in this embodiment, it can be seen that the present invention and this embodiment are not limited to a certain specific acceleration sensor probe structure, for example, the mass block-spring structure of a traditional capacitive acceleration sensor can be used , the mass block-elastic beam or mass block-elastic diaphragm structure (including porous and non-porous elastic diaphragm) of the MEMS acceleration sensor can also be used. As long as the perceived acceleration is converted into the displacement of the proof mass, and a reflective film area is made on the proof mass.

Example 2:

FIG. 2 is a schematic diagram of the structure of the fiber optic acceleration sensor probe in an embodiment of the phase carrier modulation based fiber optic acceleration sensor system of the present invention, especially showing the detailed structure of the fiber optic acceleration sensor probe 500 .

As shown in FIG. 2 , in this embodiment, the fiber optic acceleration sensor probe 500 includes an acceleration detection structure 510 , back plates 520 and 530 , an acceleration sensor frame 541 , and a fiber optic sensing head 550 .

The acceleration detection structure 510 includes a detection mass 511 , an elastic vibrating membrane 512 , a support member 513 and a reflective film area 516 on the surface of the detection mass. Wherein the proof mass 511 is located at the center of the acceleration sensor probe 500, its boundary is connected to the inner boundary of the elastic vibrating membrane 512, and the outer boundary of the elastic vibrating membrane 512 is connected to the support member 513, and passes through the support member 513 fixed on the sensor frame 541. The elastic vibrating membrane 512 is symmetrically distributed around the detection mass 511 .

The detection mass and the elastic part can adopt the mass block-spring structure of the traditional capacitive acceleration sensor, or the mass block-elastic beam or mass block-elastic vibrating membrane structure of the MEMS acceleration sensor (including porous and non-porous elastic vibrating membrane).

The reflective film area 516 refers to a small circular area made of reflective material in a broad sense, with a diameter of 10-1000 microns, generally made at the center of the surface of the detection mass 511 perpendicular to the detection acceleration direction, The reflective film region 516 may also be a square or other shaped region. The reflective film area 516 is generally made of metal aluminum or gold film. For the situation that the detection mass itself has reflection (for example, some detection mass itself is coated with a layer of aluminum film), it is not necessary to make an additional reflective film.

The back plate 520 is a relatively rigid plate whose boundary is fixed on the sensor frame 541 . Damping holes 521 of specific size and distribution are made on the back plate 520 to adjust damping. One side of the back plate 520 is made with limiting protrusions 522 to prevent overload and adhesion. A light-transmitting through hole 523 is formed in the center of the back plate 520 , and the size of the reflective film region 516 disposed on the proof mass 511 is larger than the size of the light-transmitting through hole 523 .

The proof mass 511 is parallel to the back plate 520 up and down, and the surface of the proof mass 511 where the reflective area film 516 is located is opposite to the surface of the back plate 520 where the limited convex contact 522 is made, and an air gap 542 is formed therebetween. The light-transmitting hole 523 needs to completely face the reflective film area 516 .

The back plate 530 is disposed about the proof mass 511 symmetrically to the back plate 520 . The structure of the back plate 530 can be the same as or different from the back plate 520, and damping holes 531, position-limiting protrusions 532, and light-transmitting holes 533 can also be made on it. An acoustic cavity 544 is formed between the back plate 520 and the sensor frame 541 , an air gap 543 is formed between the back plate 530 and the detection mass 511 , and an acoustic cavity 545 is formed between the back plate 530 and the sensor frame 541 . The back plate-damping hole-acoustic cavity structure formed in this way is beneficial to adjust the damping and Q value of the system.

The optical fiber sensing head 550 includes a Fizeau interference cavity holder 551 , a gradient lens 552 , and a pigtail 554 . The Fizeau interference cavity bracket 551 is fixed on the side of the back plate 520 without the limiting protrusion, forming a cylindrical Fizeau interference cavity 555 . The Fizeau interference cavity support 551 is generally made of non-metallic materials (such as plexiglass, polyvinyl chloride material, ceramics, glass, etc.), and the gradient lens 552 is fixed on the Fizeau interference cavity support 551, and its exit end surface 553 is completely opposite to the light transmission hole 523 on the back plate 520 and the reflective film area 516 on the detection mass 511 , and is guaranteed to be parallel to the light reflective film area 516 . The distance between the exit end face 553 and the reflective film area 516 , that is, the length of the Fizeau interference cavity 555 , can be adjusted by the position of the gradient lens 552 on the bracket 551 . The gradient lens 552 is connected to the transmission fiber 400 through a pigtail 554 .

The gradient lens 552 is also called a gradient index lens, or a self-focusing mirror, which can convert the transmitted light in the optical fiber into collimated light (parallel light), or couple parallel (approximately parallel) light from the outside to in single-mode fiber.

There is a layer of reflective film (such as aluminum film, silver film or magnesium fluoride film, etc.) on the outgoing end surface 553, so that the signal from the light source is partially reflected as the reference arm signal of Fizeau interference. The reflective film area 516 is used to reflect the optical signal from the gradient lens 552, and the reflected optical signal is coupled into the optical fiber through the gradient lens 552 as a sensing signal from the signal arm.

Example 3:

Fig. 3 is a schematic block diagram of an embodiment of the differential optical fiber acceleration sensor system based on phase carrier modulation of the present invention. As shown in Fig. 3, a kind of optical fiber acceleration sensor system 1000 based on phase carrier modulation of the present invention includes: laser light source 100 of phase carrier modulation, input optical fiber 200, optical fiber coupler 300, transmission optical fiber 400a, 400b, optical fiber acceleration sensor Probe 500 , output optical fiber 600 , photodetector 700 , phase carrier modulation signal electronic demodulation system 800 .

The fiber coupler 300 is connected to the phase carrier modulated laser light source 100 through the input fiber 200, connected to the fiber optic acceleration sensor probe 500 through the transmission fibers 400a, 400b, and connected to the optical fiber acceleration sensor probe 500 through the The output optical fiber 600 described above is connected to the photodetector 700 described above. The photodetector 700 is connected with the phase carrier modulation signal electronic demodulation system 800 through wires or cables.

The laser light source 100 , the input fiber 200 , the output fiber 600 , and the photodetector 700 described in this embodiment are completely the same as those in the first embodiment. The transmission optical fiber 400a, 400b described in this embodiment is completely the same as the transmission optical fiber 400 described in Embodiment 1, and the performance of the transmission optical fiber 400a, 400b should be as close to the same as possible.

The fiber coupler 300 described in this embodiment is a generalized optical coupling device. A 2x2 fiber optic coupler can be used. A beam of optical signals from the phase-carrier-modulated laser light source 100 passes through the fiber coupler 300 and enters the transmission fibers 400a and 400b respectively. At the same time, the reflected optical signal from the fiber optic acceleration sensor probe 500 and transmitted through the transmission fiber 400 a passes through the fiber coupler 300 and enters the input fiber 100 and the output fiber 600 respectively. The reflected light signal transmitted through the transmission fiber 400b also enters the input fiber 100 and the output fiber 600, and the two beams of light interfere in the output fiber 600 and are transmitted to the photodetector 700 for photoelectric conversion.

Fig. 4 is a schematic structural diagram of the fiber optic acceleration sensor probe in another embodiment of the phase carrier modulation based fiber optic acceleration sensor system of the present invention. As shown in FIG. 4 , the optical fiber acceleration sensor probe 500 described in this embodiment includes: an acceleration detection structure 510 , back plates 520 and 530 , an acceleration sensor frame 541 , and optical fiber sensing heads 550 and 560 .

The acceleration detection structure 510 includes a detection mass 511 , an elastic vibrating membrane 512 , a support member 513 and reflective film areas 516 and 517 on the detection mass. Wherein the proof mass 511 is located at the center of the acceleration sensor probe 500, its boundary is connected to the inner boundary of the elastic vibrating membrane 512, and the outer boundary of the elastic vibrating membrane 512 is connected to the support member 513, and passes through the support member 513 fixed on the sensor frame 541. The elastic vibrating membrane 512 is symmetrically distributed around the detection mass 511 .

The detection mass and the elastic part can adopt the mass block-spring structure of the traditional capacitive acceleration sensor, or the mass block-elastic beam or mass block-elastic vibrating membrane structure of the MEMS acceleration sensor (including porous and non-porous elastic vibrating membrane).

The reflective film areas 516 and 517 refer to a small circular area made of reflective material in a broad sense, with a diameter of 10-1000 microns, generally made in the center of the surface of the proof mass 511 perpendicular to the detection acceleration direction position, the reflective film regions 516 and 517 are located on the upper and lower surfaces of the proof mass 511 respectively, and are mirror-symmetrically distributed with respect to its central symmetry plane. The reflective film regions 516 and 517 may also be square or other shaped regions. The reflective film regions 516, 517 are generally made of metal aluminum or gold film. For the situation that the detection mass itself has reflection (for example, some detection mass itself is coated with a layer of aluminum film), it is not necessary to make an additional reflective film.

The back plate 520 is a relatively rigid plate whose boundary is fixed on the sensor frame 541 . Damping holes 521 of specific size and distribution are made on the back plate 520 to adjust damping. One side of the back plate 520 is made with limiting protrusions 522 to prevent overload and adhesion. A light-transmitting through hole 523 is formed in the center of the back plate 520 , and the size of the reflective film region 516 arranged on the proof mass 511 is larger than the size of the light-transmitting through hole 523 .

The proof mass 511 is parallel to the back plate 520 up and down, and the surface of the proof mass 511 where the reflective area film 516 is located is opposite to the surface of the back plate 520 where the limited convex contact 522 is made, and an air gap 542 is formed therebetween. The light-transmitting hole 523 needs to completely face the reflective film area 516 .

The back plate 530 has the same structure as the back plate 520 and is arranged symmetrically with respect to the detection mass 511 . The light-transmitting hole 533 on the back plate 530 must completely face the light-reflecting film area 517 on the detection mass 511 . An air gap 543 is formed between the back plate 530 and the proof mass 511 . An acoustic cavity 544 is formed between the back plate 520 and the sensor frame 541 , and an acoustic cavity 545 is formed between the back plate 530 and the sensor frame 541 . The back plate-damping hole-acoustic cavity structure formed in this way is beneficial to adjust the damping and Q value of the system.

The optical fiber sensing head 550 includes a Fizeau interference cavity holder 551 , a gradient lens 552 , and a pigtail 554 . The Fizeau interference cavity bracket 551 is fixed on the side of the back plate 520 without the limiting protrusion, forming a cylindrical Fizeau interference cavity 555 . The Fizeau interference cavity support 551 is generally made of non-metallic materials (such as plexiglass, polyvinyl chloride material, ceramics, glass, etc.), and the gradient lens 552 is fixed on the Fizeau interference cavity support 551, and its exit end surface 553 is completely opposite to the light transmission hole 523 on the back plate 520 and the reflective film area 516 on the detection mass 511 , and is guaranteed to be parallel to the light reflective film area 516 . The distance between the exit end face 553 and the reflective film area 516 , that is, the length of the Fizeau interference cavity 555 , can be adjusted by the position of the gradient lens 552 on the bracket 551 . The gradient lens 552 is connected to the transmission fiber 400 a through a pigtail 554 .

The gradient lens 552 is also called a gradient index lens, or a self-focusing mirror, which can convert the transmitted light in the optical fiber into collimated light (parallel light), or couple parallel (approximately parallel) light from the outside to in single-mode fiber.

There is a layer of anti-reflection film on the exit end surface 553, so that the signal from the light source and the reflected light signal can pass through the exit end surface as much as possible. It is also possible not to set any optical film on the exit end surface 553 . The reflective film area 516 is used to reflect the optical signal from the gradient lens 552, and the reflected optical signal is coupled into the optical fiber 400a through the gradient lens 552 as a sensing signal from a signal arm.

The optical fiber sensing head 560 has the same structure as the optical fiber sensing head 550 and is arranged symmetrically with respect to the proof mass 511 . The Fizeau interference cavity bracket 561 of the optical fiber sensor head 560 is fixed on the side of the back plate 530 that is not made with a limiting convex contact, between the exit end face 563 of the gradient lens 562 and the reflective film area 517 on the surface of the proof mass 511 A cylindrical Fizeau interference cavity 565 is formed, and the length of the Fizeau interference cavity 565 is exactly the same as that of the Fizeau interference cavity 555 . The gradient lens 562 is fixed on the Fizeau interference cavity support 561, and its exit end surface 563 is completely opposite to the light transmission hole 533 on the back plate 530 and the reflective film area 517 on the surface of the proof mass 511, and is guaranteed to be in direct contact with the light reflection Membrane regions 517 are parallel. The gradient lens is connected to the transmission fiber 400b through a pigtail 564 . The reflected optical signal obtained by the optical fiber sensing head 560 is coupled into the transmission optical fiber 400b through the gradient lens 562 as the sensing signal from another signal arm.

The optical fiber acceleration sensor in this embodiment works in a differential mode. When the sensor feels the effect of external acceleration, the mass block 511 in the fiber optic acceleration sensor probe 500 is displaced upwards or downwards, so that the lengths of the Fizeau interference cavities 555 and 565 are changed, and the transmission optical fibers 400a and 400b incident The laser is phase modulated. The laser light modulated by the Fizeau interference cavity 555 is input into the transmission fiber 400a as the sensing signal of one signal arm, and the laser light modulated by the Fizeau interference cavity 565 is input into the transmission fiber 400b as the sensing signal of the other signal arm, and the two are coupled through the optical fiber After being coupled by the optical device 300, it enters the output optical fiber 600 for interference, and is converted into an electrical signal by the photodetector 700, and enters the phase carrier modulation signal electronic demodulation system 800 for demodulation.

From the working principle of the optical fiber acceleration sensor with phase carrier modulation given in this embodiment, it can be seen that the present invention and this embodiment are not limited to a certain specific acceleration sensor probe structure, for example, the mass block-spring structure of a traditional capacitive acceleration sensor can be used , the mass block-elastic beam or mass block-elastic diaphragm (including porous and non-porous elastic diaphragm) structure of the MEMS acceleration sensor can also be used. As long as the perceived acceleration is converted into the displacement of the proof mass, and a reflective film area is made on the proof mass.

The differential optical fiber acceleration sensor used in this embodiment further improves the sensitivity and resolution of the sensor on the basis of Embodiment 1, and reduces its temperature coefficient of sensitivity.

Example 4:

FIG. 5 is a schematic diagram of the structure of the fiber optic acceleration sensor probe in another embodiment of the phase carrier modulation based fiber optic acceleration sensor system of the present invention, especially showing the detailed structure of the fiber optic acceleration sensor probe 500 .

As shown in FIG. 5 , the fiber optic acceleration sensor probe 500 of this embodiment includes an acceleration detection structure 510 , back plates 520 and 530 , an acceleration sensor frame 541 , and fiber optic sensing heads 550 and 560 .

The acceleration detection structure 510 includes a proof mass 511 , an elastic vibrating film 512 , a support member 513 , reflective film areas 516 and 517 on the proof mass, and driving electrodes 518 and 519 around the reflective film areas. Wherein the proof mass 511 is located at the center of the acceleration sensor probe 500, its boundary is connected to the inner boundary of the elastic vibrating membrane 512, and the outer boundary of the elastic vibrating membrane 512 is connected to the support member 513, and passes through the support member 513 fixed on the sensor frame 541. The elastic vibrating membrane 512 is symmetrically distributed around the detection mass 511 .

The detection mass and the elastic part can adopt the mass block-spring structure of the traditional capacitive acceleration sensor, or the mass block-elastic beam or mass block-elastic vibrating membrane structure of the MEMS acceleration sensor (including porous and non-porous elastic vibrating membrane).

The reflective film areas 516 and 517 refer to a small circular area made of reflective material in a broad sense, with a diameter of 10-1000 microns, generally made in the center of the surface of the proof mass 511 perpendicular to the detection acceleration direction position, the reflective film regions 516 and 517 are located on the upper and lower surfaces of the proof mass 511 respectively, and are mirror-symmetrically distributed with respect to its central symmetry plane. The reflective film regions 516 and 517 may also be square or other shaped regions. The reflective film regions 516, 517 are generally made of metal aluminum or gold film. For the situation that the detection mass itself has reflection (for example, some detection mass itself is coated with a layer of aluminum film), it is not necessary to make an additional reflective film.

The driving electrode 518 is located on the upper surface of the detection mass 511 and the periphery of the reflective film area 516, and its function is to provide an electrostatic force for the detection mass 511, which is used to adjust the position of the proof mass, introduce mechanical feedback, and Attached to provide a reverse direction of power to achieve functions such as overload recovery. The driving electrodes 519 are located on the lower surface of the proof mass 511 , and are mirror-symmetrically distributed with the driving electrodes 518 relative to the proof mass 511 .

The back plate 520 is a relatively rigid plate whose boundary is fixed on the sensor frame 541 . Damping holes 521 of specific size and distribution are made on the back plate 520 to adjust damping. One side of the back plate 520 is made with limiting protrusions 522 to prevent overload and adhesion. A light-transmitting through hole 523 is formed in the center of the back plate 520 , and the size of the reflective film region 516 disposed on the proof mass 511 is larger than the size of the light-transmitting through hole 523 . A drive electrode 524 is formed on the surface of the back plate 520 opposite to the proof mass 511 , which forms a drive electrode pair with the drive electrode 518 on the proof mass 511 to provide electrostatic force for the proof mass 511 .

The proof mass 511 is parallel to the back plate 520 up and down, and the surface of the proof mass 511 where the reflective area film 516 is located is opposite to the surface of the back plate 520 where the limited convex contact 522 is made, and an air gap 542 is formed therebetween. The light-transmitting hole 523 needs to face the reflective film area 516 completely, and the driving electrodes 518 and 524 need to face as far as possible.

The back plate 530 has the same structure as the back plate 520 and is arranged symmetrically with respect to the detection mass 511 . The light transmission hole 533 on the back plate 530 must completely face the reflective film area 517 on the proof mass 511 , and the drive electrode 534 must face the drive electrode 519 on the proof mass 511 as much as possible. An air gap 543 is formed between the back plate 530 and the proof mass 511 . An acoustic cavity 544 is formed between the back plate 520 and the sensor frame 541 , and an acoustic cavity 545 is formed between the back plate 530 and the sensor frame 541 . The back plate-damping hole-acoustic cavity structure formed in this way is beneficial to adjust the damping and Q value of the system.

The optical fiber sensing head 550 includes a gradient lens 552 and a pigtail 554 . The gradient lens 552 is fixed on the top cover of the acceleration sensor housing, and a Fizeau interference cavity 555 is formed between the exit end surface 553 of the gradient lens 552 and the reflective film area 516 on the detection mass 511 . The exit end surface 553 of the gradient lens 552 is completely opposite to the light transmission hole 523 on the back plate 520 and the reflective film area 516 on the detection mass 511 , and is guaranteed to be parallel to the light reflective film area 516 . The distance between the exit end face 553 and the reflective film area 516 , that is, the length of the Fizeau interference cavity 555 , can be adjusted by the position of the gradient lens 552 on the top cover of the acceleration sensor housing. The gradient lens 552 is connected to the transmission fiber 400 a through a pigtail 554 .

The gradient lens 552 is also called a gradient index lens, or a self-focusing mirror, which can convert the transmitted light in the optical fiber into collimated light (parallel light), or couple parallel (approximately parallel) light from the outside to in single-mode fiber.

There is a layer of anti-reflection film on the exit end surface 553, so that the signal from the light source and the reflected light signal can pass through the exit end surface as much as possible. It is also possible not to set any optical film on the exit end surface 553 . The reflective film area 516 is used to reflect the optical signal from the gradient lens 552, and the reflected optical signal is coupled into the optical fiber 400a through the gradient lens 552 as a sensing signal from a signal arm.

The optical fiber sensing head 560 has the same structure as the optical fiber sensing head 550 and is arranged symmetrically with respect to the proof mass 511 . The gradient lens 562 is fixed on the bottom cover of the acceleration sensor housing, and the formed Fizeau interference cavity 565 has the same length as the Fizeau interference cavity 555 . The exit end surface 563 of the gradient lens 562 is completely opposite to the light transmission hole 533 on the back plate 530 and the reflective film area 517 on the detection mass 511 , and is guaranteed to be parallel to the light reflective film area 517 . The gradient lens is connected to the transmission fiber 400b through a pigtail 564 . The reflected optical signal obtained by the optical fiber sensing head 560 is coupled into the transmission optical fiber 400b through the gradient lens 562 as the sensing signal from another signal arm.

When the optical fiber acceleration sensor is working, a feedback control circuit module needs to be added in the electronic demodulation system 800 of the phase carrier modulation signal, and the module is connected to the driving electrodes 518, 519, 524, 534 on the fiber optic acceleration sensor probe 500 . The phase carrier modulation signal electronic demodulation system 800 generates voltage feedback signals proportional to the received signal amplitudes and inputs them to the electrodes 518, 519, 524, 534 while performing demodulation.

The differential fiber optic acceleration sensor with feedback provided in this embodiment can further adjust system parameters and improve its sensitivity and dynamic range on the basis of the original fiber optic acceleration sensor. Moreover, the gradient lens of the differential optical fiber acceleration sensor with feedback provided in this embodiment is fixed on the housing of the acceleration sensor, which can simplify the system structure.

Example 5:

FIG. 6 is a schematic structural diagram of the fiber optic acceleration sensor probe in another embodiment of the phase carrier modulation based fiber optic acceleration sensor system of the present invention, especially showing the detailed structure of the fiber optic acceleration sensor probe 500 .

As shown in Figure 6, the optical fiber acceleration sensor probe 500 provided in this embodiment is a single crystal silicon acceleration sensor probe based on MEMS technology, including a single crystal silicon acceleration detection structure 510, printed circuit back plates 520 and 530, an acceleration sensor Frame 541, optical fiber sensor heads 550 and 560.

The acceleration detection structure 510 is a single crystal (100) oriented silicon wafer, which is manufactured through MEMS process steps such as high temperature oxidation, photolithographic patterning, dethermal oxygen removal, and bulk etching.

The bottom view of the monocrystalline silicon support structure 513 is circular, used to support the acceleration detection structure and bonded to the printed circuit back plate 520, 530, and its thickness is about the same as that of the monocrystalline (100) oriented silicon wafer .

The bottom view of the single crystal silicon elastic vibrating membrane 512 is circular, and the bottom view of the single crystal silicon acceleration detection mass 511 is circular, both of which are processed by bulk etching of the single crystal (100) oriented silicon wafer . The single crystal silicon acceleration detection mass 511 has the same geometric center as the single crystal silicon elastic vibrating membrane 512, the outer boundary of the single crystal silicon elastic vibrating membrane 512 is connected with the inner boundary of the single crystal silicon support structure 513, and the inner boundary It is connected with the outer boundary of the single crystal silicon acceleration proof mass 511 .

In addition, the bottom view of the single crystal silicon support structure 513, the single crystal silicon elastic diaphragm 512 and the single crystal silicon acceleration detection mass 511 may also be in other shapes such as rectangle, square, regular hexagon, etc. Those skilled in the art can Choose according to design needs and process conditions.

Due to the double-sided etching process, the acceleration detection structure 510 is mirror-symmetrical with respect to the central plane in the thickness direction. Wherein, the thickness of the single crystal silicon supporting structure 513 is approximately equal to the thickness of the single crystal (100) oriented silicon wafer. The thickness of the single-crystal silicon acceleration detection mass 511 is thinner than that of the single-crystal (100) oriented silicon wafer, and the vertical distances between its upper and lower surfaces and the upper and lower surfaces of the single-crystal silicon support structure 513 are about 2 to 100 microns. The thickness of the single crystal silicon elastic diaphragm 512 is 5-500 microns. The above-mentioned distance and thickness can also be adjusted according to the needs of structural design.

Reflective film regions 516 and 517 are also formed on the single crystal silicon detection mass of the acceleration detection structure 510 , and driving electrodes 518 and 519 around the reflective film regions are formed. A layer of aluminum film may also be plated on the acceleration detection structure 510 to form the reflective film regions 516 , 517 and the driving electrodes 518 , 519 .

The printed circuit back plate 520 is a rigid printed circuit board. A certain number and distribution of damping holes 521 are made on the back plate 520 , and a light-transmitting through hole 523 is punched at the center of the back plate 520 . On the lower surface of the back plate 520 , a position-limiting protrusion 522 is made, and a driving electrode 524 is plated, and the electrode is connected to a via hole 525 penetrating through the back plate 520 . The other end of the via hole 525 is connected to the lead wire and the pad 526 on the upper surface of the back plate 520 for receiving the driving voltage.

The structure of the via hole 528 on the back plate 520 is exactly the same as that of the via hole 525. It is connected to the electrode 527 on the lower surface, and is further electrically connected with the drive electrodes 518, 519 on the single crystal silicon acceleration detection structure 510. Located on the upper surface, it is connected with leads and pads 529 so as to provide driving voltages for the driving electrodes 518 and 519 .

The shape and area of the electrodes 524 and 527, the shape, size and distribution of the damping hole 521, the shape, size and height of the limiting protrusion 522, and the size of the via holes 525 and 528 can be determined by this Those skilled in the art can design as needed.

The detection mass 511 is parallel to the back plate 520 up and down, and the surface where the reflective area film 516 on the detection mass 511 is opposite to the surface of the limited convex contact 522 made on the back plate 520, and an air gap of 2 to 100 microns is formed therebetween 542. The light-transmitting hole 523 needs to face the reflective film area 516 completely, and the driving electrodes 518 and 524 need to face as far as possible.

The back plate 530 has the same structure as the back plate 520 and is arranged symmetrically with respect to the detection mass 511 . The driving electrodes 534 on the back plate 530 and the driving electrodes 519 on the proof mass should face as directly as possible. An air gap 543 is formed between the back plate 530 and the proof mass 511 . An acoustic cavity 544 is formed between the back plate 520 and the sensor frame 541 , and an acoustic cavity 545 is formed between the back plate 530 and the sensor frame 541 . The back plate-damping hole-acoustic cavity structure formed in this way is beneficial to adjust the damping and Q value of the system.

The optical fiber sensing head 550 includes a Fizeau interference cavity holder 551 , a gradient lens 552 , and a pigtail 554 . The Fizeau interference cavity bracket 551 is fixed on the side of the printed circuit back plate 520 where no limiting protrusions are made to form a cylindrical Fizeau interference cavity 555 . The Fizeau interference cavity support 551 is generally made of non-metallic materials (such as plexiglass, polyvinyl chloride material, ceramics, glass, etc.), and the gradient lens 552 is fixed on the Fizeau interference cavity support 551, and its exit end surface 553 is completely opposite to the light transmission hole 523 on the back plate 520 and the reflective film area 516 on the detection mass 511 , and is guaranteed to be parallel to the light reflective film area 516 . The distance between the exit end face 553 and the reflective film area 516 , that is, the length of the Fizeau interference cavity 555 , can be adjusted by the position of the gradient lens 552 on the bracket 551 . The gradient lens 552 is connected to the transmission fiber 400 a through a pigtail 554 .

The gradient lens 552 is also called a gradient index lens, or a self-focusing mirror, which can convert the transmitted light in the optical fiber into collimated light (parallel light), or couple parallel (approximately parallel) light from the outside to in single-mode fiber.

There is a layer of anti-reflection film on the exit end surface 553, so that the signal from the light source and the reflected light signal can pass through the exit end surface as much as possible. It is also possible not to set any optical film on the exit end surface 553 . The reflective film area 516 is used to reflect the optical signal from the gradient lens 552, and the reflected optical signal is coupled into the optical fiber 400a through the gradient lens 552 as a sensing signal from a signal arm.

The optical fiber sensing head 560 has the same structure as the optical fiber sensing head 550 and is arranged symmetrically with respect to the proof mass 511 . The Fizeau interference cavity bracket 561 of the optical fiber sensor head 560 is fixed on the side of the back plate 530 that does not make a limiting convex contact, forming a cylindrical Fizeau interference cavity 565, and the Fizeau interference cavity 565 is connected to the Fizeau interference cavity The lengths of the interference cavities 555 are exactly the same. The gradient lens 562 is fixed on the Fizeau interference cavity bracket 561, and its exit end surface 563 is completely opposite to the light transmission hole 533 on the back plate 530 and the reflective film area 517 on the proof mass 511, and is guaranteed to be in direct contact with the reflective film Regions 517 are parallel. The gradient lens is connected to the transmission fiber 400b through a pigtail 564 . The reflected optical signal obtained by the optical fiber sensing head 560 is coupled into the transmission optical fiber 400b through the gradient lens 562 as the sensing signal from another signal arm.

This embodiment provides a MEMS-based single-crystal silicon feedback differential optical fiber acceleration sensor. The MEMS process is used to manufacture the acceleration sensor detection structure. The advantages.

Embodiment 6:

This embodiment provides a detailed structure of the optical fiber acceleration sensor probe 500 manufactured by the full MEMS process of another embodiment of the phase carrier modulation based optical fiber acceleration sensor system of the present invention.

The MEMS process-based acceleration sensor with an acoustic cavity provided in this embodiment has a structure similar to that of the acceleration sensor provided in Embodiment 5. Among them, the single crystal silicon acceleration detection structure is exactly the same. It's just that the material of the back plate is changed from a printed circuit board to a glass plate (such as Pyrex glass). The thickness of the glass plate is 300-1000 microns. The damping through hole and the light transmission hole are formed on the glass plate through the ultrasonic drilling process. Leads, pads and driving electrodes are formed on the board. A limiting convex contact is formed on the glass plate by a lift-off process.

After the preparation of the back plate is completed, the optical fiber sensing head 550, 560 can be fixed on the glass back plate 520, 530 through the MEMS bonding process, and then the back plate 520, 530 can be further bonded through the anodic bonding process. Bond with the acceleration detection structure 510 .

The processes of punching holes, forming via electrodes, forming position-limiting protrusions, and bonding are not limited to the processes mentioned in this embodiment, and those skilled in the art can also realize the same structure through other processes.

The acceleration sensor adopting the acceleration sensor probe structure provided by this embodiment is completely manufactured by MEMS processing technology, which can further improve the sensitivity, reduce the volume of the sensor, realize integration with subsequent circuits, and realize miniaturization.

Claims (10)

1. An optical fiber acceleration sensor probe, is characterized in that, comprises: acceleration detection structure, at least one back plate, acceleration sensor frame and at least one optical fiber sensing head, The acceleration detection structure is located at the center of the acceleration sensor probe, and its composition includes: a detection mass, an elastic component and a supporting component located around the detection mass, the detection mass is located at the center of the entire acceleration detection structure, and the elastic The two ends of the component are respectively connected to the detection mass and the support component, the elastic component is a spring, a continuous membrane, a membrane with holes or a plurality of elastic beams, and is symmetrically distributed around the detection mass, The support component is used to support the acceleration detection structure and fix it on the acceleration sensor frame; The detection mass is parallel to the back plate up and down, an air gap is formed therebetween, and a reflective film area is made on the surface of the proof mass on the side opposite to the back plate, and the reflective film area is located on the detection mass. the center of the block or cover the entire surface of the proof mass; The back plate is a rigid plate whose boundary is fixed on the acceleration sensor frame, and damping holes of a specific size and distribution are made on the back plate to adjust damping, and one side of the back plate is made There are limited convex contacts to prevent overload and adhesion. In addition, a light-transmitting hole is made in the center of the back plate to transmit incident and reflected laser light; an acoustic cavity is formed between the back plate and the acceleration sensor frame. The acoustic cavity is a cavity or two connected or disconnected cavities, which are used to form a flow gas circuit and improve the frequency response of the system; Yes, and the size of the reflective film area is larger than the size of the light transmission hole; The optical fiber sensing head includes a gradient lens and a pigtail, the pigtail is installed at the tail of the gradient lens, the gradient lens is installed on the acceleration sensor frame, or is installed on an additional Fizeau interference cavity support, When installing, make the exit end surface of the gradient lens face the light transmission hole on the back plate and the reflective film area on the detection mass block, and ensure that the exit end surface is parallel to the reflective film area, through which the reflective film area will pass through the The incident laser light of the gradient lens is reflected back, thereby modulating the phase of the incident light, and a cylindrical Fizeau interference cavity is formed between the exit surface of the gradient lens and the region of the reflective film. 2. fiber optic acceleration sensor probe as claimed in claim 1, is characterized in that, There are two back plates, and the two back plates are arranged symmetrically up and down relative to the proof mass. The two back plates have the same structure, and damping holes, limiting protrusions and light transmission holes are made on them. , the two back plates respectively form two upper and lower acoustic cavities with the acceleration sensor frame, and form two upper and lower air gaps with the proof mass, thus forming a back plate-damping hole-acoustic cavity structure To adjust the damping and Q value of the system; The upper and lower surfaces of the detection mass are provided with reflective film areas, and are mirror-symmetrically distributed with respect to the detection mass; There are two optical fiber sensing heads with the same structure, and they are arranged symmetrically on the acceleration sensor frame with respect to the detection mass, or on the additionally added Fizeau interference cavity support, and make the gradient The exit end surface of the lens is directly opposite to the light transmission hole on the back plate and the reflective film area on the detection mass block, and is guaranteed to be parallel. The lengths of the upper and lower Fizeau interference cavities are exactly the same. 3. fiber optic acceleration sensor probe as claimed in claim 1, is characterized in that, The acceleration detection structure also includes driving electrodes, which are arranged on the periphery of the reflective film area on one or the upper and lower surfaces of the detection mass. If the upper and lower surfaces of the detection mass are provided, the two driving electrodes are relatively The proof masses are distributed mirror-symmetrically, The back pole plate has two pieces, and the driving electrode is also made on the surface of the back pole plate opposite to the detection mass block, which is as direct as possible to the drive electrode on the detection mass block to form a drive electrode pair, for The detection mass provides electrostatic force, which is used to adjust the position of the mass, introduce mechanical feedback, and provide an electric power in the opposite direction to achieve overload recovery when the overload adheres, There are one or two optical fiber sensor heads, which are arranged on the acceleration sensor frame, or on the Fizeau interference cavity support added in addition, and make the outgoing end face of the gradient lens and the transparent lens on the back plate The light hole and the area of the reflective film on the detection mass block are facing each other, and the exit end surface is guaranteed to be parallel to the area of the reflective film; when two optical fiber sensing heads are set, they are set symmetrically about the proof mass block, and the upper and lower two optical fibers The two upper and lower Fizeau interference cavities formed between the gradient lens exit surface of the sensor head and the reflective film region have exactly the same length. 4. The optical fiber acceleration sensor probe according to any one of claims 1 to 3, wherein the reflective film area arranged on the detection mass is circular, square or other arbitrary shapes, and its material is made of aluminum film Any reflective film including gold film. 5. The optical fiber acceleration sensor probe according to any one of claims 1 to 3, characterized in that, When two optical fiber sensor heads are provided, a layer of anti-reflection coating is provided on the exit end surface of the gradient lens, so that the signal from the light source and the reflected light signal can pass through the exit end surface as much as possible; When one optical fiber sensor head is provided, a reflective film is coated on the exit end surface of the gradient lens to reflect a part of the incident light back into the pigtail. 6. The optical fiber acceleration sensor probe according to any one of claims 1 to 3, wherein the acceleration detection structure adopts a single-crystal oriented silicon wafer, which includes high-temperature oxidation, photolithographic patterning, and thermal oxygen removal. and bulk etched MEMS process steps, The single crystal silicon acceleration detection structure includes three parts: a single crystal silicon support structure, a single crystal silicon elastic vibrating membrane and a single crystal silicon acceleration detection mass block, wherein the single crystal silicon acceleration detection mass block and the single crystal silicon elastic vibration The membrane has the same geometric center, and the two are processed by volume etching of the single crystal oriented silicon wafer, and the inner boundary of the single crystal silicon elastic vibration membrane is connected with the outer boundary of the single crystal silicon acceleration detection mass , the outer boundary of the single crystal silicon elastic diaphragm is connected to the inner boundary of the single crystal silicon support structure, and the single crystal silicon support structure is used to support the acceleration detection structure and is attached to the back plate; The bottom view of the single crystal silicon support structure, the single crystal silicon elastic diaphragm and the single crystal silicon acceleration detection mass is any shape including circle, rectangle, square and regular hexagon; The monocrystalline silicon acceleration detection structure is mirror-symmetrical to the central plane in the thickness direction, wherein the thickness of the monocrystalline silicon support structure is equal to the thickness of the single-crystal oriented silicon wafer, and the thickness of the monocrystalline silicon acceleration detection mass is smaller than that of the monocrystalline silicon acceleration detection mass. The thickness of the single crystal oriented silicon wafer is thin, the vertical distances between the upper and lower surfaces of the single crystal silicon support structure and the upper and lower surfaces of the single crystal silicon supporting structure are respectively about 2-100 microns, and the thickness of the single crystal silicon elastic diaphragm is 5-500 μm. Microns. 7. The optical fiber acceleration sensor probe according to any one of claims 1-3, wherein the material of the back plate is a printed circuit board, a silicon wafer or a glass plate. 8. The optical fiber acceleration sensor probe according to claim 7, wherein the glass plate is Pyrex glass with a thickness of 300-1000 microns, and damping through holes and light-transmitting holes are formed on the glass plate through an ultrasonic drilling process , forming via-hole electrodes on the glass plate by electroplating process, forming leads, pads and driving electrodes on the glass plate by evaporation or sputtering process, forming position-limiting bumps on the glass plate by lift-off process, and back electrode After the plate is prepared, the optical fiber sensor head can be fixed on the glass back plate by MEMS bonding process, and then the back plate and the acceleration detection structure can be bonded by anodic bonding process. 9. A fiber optic acceleration sensor system, characterized in that it is a fiber optic acceleration sensor system based on phase carrier modulation, including: laser light source, optical fiber, fiber optic coupler, acceleration sensor probe, photodetector and phase carrier modulation signal electronic demodulation system, Wherein, the laser light source is a phase carrier modulated laser light source, including at least one semiconductor laser and an oscillator that generates a modulation current. Within the rated luminous power range, the frequency of the laser light output by the semiconductor laser varies with the modulation current linear change; The optical fiber is used for low-loss transmission of optical signals, including: an input optical fiber, a transmission optical fiber and an output optical fiber, all of which are single-mode optical fibers, and are polarization-maintaining single-mode optical fibers or non-polarization-maintaining single-mode optical fibers; The fiber coupler is connected to the laser light source modulated by the phase carrier through the input fiber, connected to the acceleration sensor probe through the transmission fiber, and connected to the photodetector through the output fiber. The optical signal from the laser light source is coupled into the transmission optical fiber, and the reflected optical signal from the optical fiber acceleration sensor probe is coupled into the output optical fiber; The acceleration sensor probe has the acceleration sensor probe structure according to any one of claims 1 to 8, and is connected to the transmission optical fiber through a pigtail connected to the tail of the gradient lens; The photodetector is a photoelectric conversion circuit composed of a PIN photodiode, which converts the received optical signal from the fiber coupler into an electrical signal proportional to the light intensity, and transmits the electrical signal to the Phase carrier modulation signal electronic demodulation system, which is connected with the phase carrier modulation signal electronic demodulation system by wire or cable; The phase carrier modulation signal electronic demodulation system is an electronic signal processing system that demodulates the corresponding acceleration signal in the carrier modulation signal, and converts the electrical signal corresponding to the acceleration value from the electrical signal from the photodetector to After demodulation, the demodulation methods include: analog electronic circuit demodulation scheme and digital signal processing DSP demodulation scheme. 10. The fiber optic acceleration sensor system as claimed in claim 9, wherein the fiber optic coupler is a coupler that divides the injection beam into two beams of light with equal light intensity, when an optical fiber transmission is used in the acceleration sensor probe When the sensor head is used, only one of the two beams of light from the fiber coupler enters the sensor probe, and the other beam is discarded; when two fiber sensor heads are used in the acceleration sensor probe, the fiber coupler divides The two beams of light that come out enter the two optical fiber sensing heads respectively, and the two beams of light realize differential detection.

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